1. Field of the Invention
The present invention relates broadly to telecommunication network systems. More particularly, the present invention relates to an intelligent data service unit (DSU) located in a managed telecommunications network.
2. State of the Art
Data service units (DSUs) are common elements in telecommunications networks today and basically serve as the termination point of a digital subscriber loop (e.g., a termination for a digital data service (DDS) line defined in ANSI T1.410). As seen in a typical prior art configuration of FIG. 1, the data service unit 12 sits between a service provider 14 and a router 16 and provides an interface (e.g., DDS or frame relay interface) between a four-wire metallic subscriber loop 17 of the service provider and the wide area network (WAN) interface 18 of the router. In other words, in one direction, the DSU 12 receives bipolar-return-to-zero data on a DDS line and converts it into WAN-compatible data; and in the other direction the DSU 12 receives WAN data and converts it for output onto the digital subscriber loop (i.e., the subscriber/service provider "line") The router is often coupled to one or more local area networks (LANs) 20, each typically having multiple user terminals 24. The function of the router is to take the data provided by the DSU (e.g., WAN formatted data) and convert it into high speed local area network (LAN) traffic (often using Ethernet or token ring protocol). Thus, the router establishes a dialog between itself and the service provider. This dialog is typically called a "session", and may be a session governed by a standard protocol (e.g., PPP or Frame Relay described in ANSI T1.618 and ITU-T Q922) or a proprietary protocol. In any case, a data link connection (e.g., PPP, HDLC, or Frame Relay) is established between the two nodes, allowing for network IP connections to occur between multiple LANs sharing the same service provider, one of which is used by the management station.
The customer equipment of FIG. 1 is managed by a network management station 30 coupled to the service provider (i.e., the "cloud") 14. The function of the network management station 30 is to determine what equipment is coupled to the network, to configure that equipment, to obtain alarm information and network statistical information, and to run diagnostic tests on the equipment in the network. In carrying out its functions, the network management station typically runs programs according to a protocol such as SNMP (simple network management protocol), or any other protocol such as TCP (transmission control protocol), ICMP (internet control message protocol) which runs atop the Internet Protocol (IP) packet environment.
It is well accepted in the art that DSUs are "dumb terminals"; i.e., they simply reformat all incoming data to an outgoing frame and signal format, and take no action based on the contents of the customer data; although some DSUs can respond to service provider test commands such as DSU/CSU loop backs and V.54/PN127 loop initiation sequences. Thus, in order to manage the DSU from a network management station, for configuration or diagnostic purposes, it is necessary to send an IP packet from the network management station 30 through the service provider 14, through the DSU 12, through the router 16, and to the LAN 20, and to provide the DSU with a terminal server (i.e., LAN to serial interface equipment--not shown) or a direct LAN interface port 32 so that it can receive the IP packet from the LAN in an out-of-band manner. While this arrangement, if provided, can be used to effectively configure the DSU and can be used to obtain diagnostic information, it suffers from various drawbacks. First, should the router or LAN fail, there is no manner of remotely managing the DSU, as management of the DSU is via the router and LAN. Thus, management of the DSU will be interrupted precisely when it might be most needed. Second, the hardware of the DSU must be changed for each type of LAN utilized, as the DSU must be provided with its own SLIP/PPP serial connection and port or MAC interface hardware and MAC address as well as its own LAN IP and gateway IP and MAC address. Third, it will be appreciated that this extra hardware adds a significant cost to the DSU.